Production of high viscosity index lubricating oils



June 23, 1953 A. T. wATsoN ET AL PRODUCTION OF HIGH VISCOSITY INDEX LUBRICATING OILSA Filed March 26, 1952 Patented June 23, 19.53

PRODUCTION OF HIGH VISCOSITY INDEX LUBBICATING OILS Albert T. Watson and Sam H. Hastings, Baytown, Tex., assignors, by mesne assignments, to yStandard Oil Development Company, Elizabeth, N. J., a corporation of Delaware Application March 26, 1952, Serial No. 278,548

45 Claims.

The present invention is Idirected to a method of producing high viscosity index lubricating oils. More particularly, the invention is directed to a `method by Which deleterious lubricating oil components are removed from a lubricating oil fraction containing them. In its more `specific aspects, the invention is directed to a three-stage adsorptive separation process in which a llubricating oil fraction containing beneficial and detrithe lubricating .oil are adsorbed preferentially with the predominantly saturated lubricating oil components being non-adsorbed. yOn charging of .the aromatic hydrocarbon fraction, which has a .boiling point lower than the boiling point of the lubricating oil fraction, the aromatic hydrocarbon fraction .is adsorbed and the aromatic lubricating oil componentsare desorbed allowing them to be recovered.

mental components is `separated selectively into 1U The predominantly saturated lubricating oil the 'benencial components and the detrimental component which Will include parafflins, .C011- cornponents and the former recovered. densed vand single ring naphthenes, is then The invention maybe `describedbrieiiy as incharged to a bed of activated carbon and the volving Va method for producing high viscosity y feed thereto alternated with a paranie hydroindex lubricating oil from a lubricatingoil frac- 1" Carbon Solvent having' a boiling point lOWeI than tion lcontaining condensed ring naphthenic and the boiling point of the lubricating Oil fraction condensed ring aromatic hydrocarbons in adand the boiling .point f the alolnaiie hydromixture with parainnic and single ring naphcarbon fraction. By alternately Charging the thenic and single ring aromatic hydrocarbons in predominantly Saturated lubricating Oil Coln- Which the condensed `ring naphthenic and the 2o Donent and the parafdnic hydrocarbon solvent condensed ring aromatic hydrocarbons are reto the bed of activated Carbon the Single ring moved and a lubricating oil containing substannophthenio and the Forattini@ hydrocarbons are tially only parafhnic and single vring naphthenio selectively adsorbed and the condensed ring and single ring aromatic hydrocarbons is renabhthenio hydrocarbons are substantially un- Covered, adsorbed, allowing a separation to be made and 'The invention involves .also a method for protWo flaetlons t0 be .TeCOVeled from the bed of ducing high viscosity inde-x lubricating ,oil .in Carbon alternately, one vflaotion Containing Con- Which a lubricating oil fraction containing parafdensodnephtnenie hydlooelbon Components and nnic, single and condensed ring naphthenic and the other fleotion Containing Dorallnio and single and condensed ring aromatichydrocarbons `3Q .Single Yling nanlltllenie lllbliegting Oil Colnis separated into a first fraction containing preponentedominantly saturated lubricating oil components The V131"eflolnlnantly aromatlc hydrocarbon and a second Afraction containing predominantly vfleotol TeooVeled from the bed 0f `Silioi gel iS `aromatic .lubricating oil components. The rst Charged .to e bed of alumina gel and the feed fraction is separated into a third fraction conthereto eltelloted Wltll'an arolnotie hydrocarbon taining condensed ring naphthenic lubricating fleotlon hofVmg e bollmg p olnt lower' than the oil components and afourth fraction containing boiling Polllt Of the .lulollotilg oil fleetion parainmo and single ring naphthenio lubricating whereby the predominantly aromatic lubricating oil components. The second fraction is separated .oil Component 1S Separated Into a fraction coninto a `fifth fraction containing single ring aro-v 40 taining Singlelg eromatiolublioatng oil commatic lubricating oil fractions and a sixth frac- .Bonoloto ond .onotche'vfmotloll Containing Colltion containing condensed ringaromatic lubricatdensod lmg lubloetmg oll Components, the ing oil components. The fourth and fifth fracalumina gel ladsorbirls selectively the Condensed tions are combined and there is recovered from ring atl.omttlo lubricating oil Components .Which the combined fourth and fth fractions la lubriare dosorbed by the aromatic hydooalbol freelcating oil o'f high `viscosity index, higher than that producible in conventional operations.

The invention maybe practiced vsuch that .the lubricating oil fraction is separated into a predominantly saturated lubricating oil component and a predominantly aromatic lubricating oil component by charging the lubricating oil fraction and an aromatic hydrocarbon fraction alternately to a bed of silicagel, vsuch ,that-thepredominantly varomatiecontaining components in tion which, in turn, is adsorbed by the alumina gel resulting `in the alternate recovery kfrom the bedof fractions containing single ring aromatic lubricating oil components in one instance and jectedto arecoi/.ery operation, .such .as a distillation operation to allow recovery of a finished lubricating oil fraction consisting substantially of single ring aromatic and single ring naphthenic hydrocarbons and parainic hydrocarbons.

The slica gel employed in the practice of the present invention will be the silica gel of commerce having a mesh in the range from about 14 to about 250 mesh but which may range as high as 350 mesh. Silica gel is a well known article of commerce and further description thereof need not be given here.

The activated carbon or activated charcoal, as it is sometimes termed, may be obtained from a large number of well known sources. For example, the activated carbon or charcoal may be prepared from bagasse, kelp, fruit pits, coconuts, farm products, such as corn cobs, cereals, waste cellulosic material, blood, petroleum acid sludges, petroleum residues and many other materials too numerous to mention here. The activated carbon or charcoal is used in a sense that it has been activated and will adsorb selectively hydrocarbons by types. Methods of activating carbon or charcoal are well known and since these methods do not form part of the invention they will not be described here. The activated carbon or charcoal will have mesh sizes comparable to that specied for silica gel.

The alumina gel will suitably be activated alumina and may be prepared by any ofthe methods well known to the art, such as, for eX- ample, by heating alpha alumina trihydrate to drive off combined water, or by drying and heating the gel formed by precipitation or' A1Cl3 with ammonia or alkali. See also Encyclopedia of chemical technology edited by R. E. Kirk and Donald F. Othmer, the Interscience Encyclopedia Inc., New York, 1947, vol. I, pp. 642-3. The alumina gel will have mesh sizes comparable to that of the silica gel and the activated charcoal. Y.

The invention will suitably be practiced at temperatures in the range from about 60 up to about 120 F. with preferred temperatures in the range from about 80 to about 100 F.

The several porous adsorbents including silica gel, activated carbon and alumina gel may suitably be used in beds and particularly in elongated vertical beds. It is desirable to provide the beds having a length to diameter ratio in the range from about 1:1 to about 200:1 with length to diameter ratios in the range from about 3 to about 100:1 being preferred. Good results may be obtained with length to diameter ratios of about 14 to 28:1. It may also be desirable 'to provide suitable internal baffling equipment, such as a vertical and horizontal baffles, in the columns to prevent channeling and also to allow contact between the streams owing through the bed and the porous adsorbent; in fact, the beds may be suitably partitioned to provide in one particular bed a plurality of small beds having high ratios of length to diameter.

In view of the viscous nature of the lubricating oil fraction which might make the process of the present invention unattractive due to slow flow through the beds and in View of the upper temperature limit of 120 F. in which satisfactory separation is effected, it is desirable to admix the lubricating oil fraction with a naphthenic solvent or fraction boiling in the range from about 100 to about 360 F. This naphthenic solvent may contain hydrocarbons having carbon atoms in the molecule. The naphthenic hydrocarbon solvent, it will be clear, boils below the boiling point of the lubricating oil fraction.

The aromatic hydrocarbon fraction which is charged alternately to the beds of silica gel and alumina gel is suitably a toluene concentrate boiling in the range from about to about 320 F. and containing approximately 50 to 100% of toluene but may be a xylene-containing fraction, if desired. When the aromatic hydrocarbon fraction is a toluene concentrate it will have a boiling point lower than the naphthenic hydrocarbon fraction.

The paraffmic hydrocarbon fraction which is charged alternately to the bed of activated carbon suitably has a boiling point in the range from 80 to 310 F. and should boil below the boiling point of the naphthenic hydrocarbon fraction.

The present invention will be further illustrated by reference to the drawing in which the single figure is a flow diagram of a preferred mode of operation.

Referring now to the drawing numeral II designates a charge tank which contains, for example, a dewaxed lubricating oil fraction which is introduced into the system by line I2 containing pump I3 and valve I4. By operating pump I3 and opening valve I4 the lube fraction is pumped through line I2. Line I2 is joined by line I5 which connects to tank I6 which contains a naphthenic hydrocarbon fraction which is introduced by line I5 containing pump I'I and valve I8 to adjust the viscosity of the lube fraction in line I2. Grdinarily the ratio of lube fraction to naphthenic hydrocarbon fraction will be about 1:2 but other ratios may be employed depending on the viscosity of the lube fraction. It should be suicient to say that a suiiicient amount of the naphthenic hydrocarbon fraction should be introduced by line I5 into line I2 to provide a viscosity of the admixture in the range from about 30 to 200 SSU which will allow the mixture to iiow readily through adsorption column I9 which contains a bed of silica gel 20 indicated generally by the shaded portion.

The admixture of lube fraction and the naphthenic hydrocarbon flows through line I2 controlled by valve 2I into branch line 22 and thence downwardly through the bed of silica gel resulting in the selective adsorption of the predominantly aromatic components in the lube fraction. After the capacity of the silica gel for the aromatics present in the lube fraction is used, W through lines I2 and I5 is discontinued by shutting down pumps I3 and Il and closing valves I4 and I8, valve 2I being also closed. At this point in the operation, an aromatic hydrocarbon fraction, such as a toluene concentrate, is introduced into the system from tank 23 and through line 24 containing .pump 25. Line 24 connects into line 26 which also connects into line 22. The valve 2'! in line 26 is in the open position and allows flow from tank 23 through lines 24, 26 and 22. The toluene concentrate serves to desorb the aromatic lubricating oil components adsorbed on the silica. gel bed 20 with the aromatics in the toluene concentrate being adsorbed selectively. These operations are alternated such that there is recovered from the adsorption zone I9 by line 2B controlled by valve 29 a first fraction and a second fraction. The first fraction contains the substantially saturated lubricating oil components which are discharged by line 30 controlled by valve 3I into a distillation zone 32, while the second fraction is alternately discharged by line 33 controlled by valve 34 into distillation tower 35. The second fraction contains the aromatic lubricating S cil .components'in admixture with the naphthenic hydrocarbon land the toluene concentrate while the saturated lubricating oil components introduced into distillation tower 32 contains naphthenic hydrocarbon and toluene concentrate. In distillation zone 32 which is a conventional distillation apparatus and which is contemplated will be provided with all auxiliary equipment necessary for such operation, the'predominantly saturated fraction is distilled to recover therefrom the toluene concentrate which is withdrawn as an overhead fraction through line 36 and routed thereby back into tank 23, the saturated lubricating oil components in admixture with the naphthenic hydrocarbon fraction being discharged by line 31 into a stock vtank 38 from Which this fraction is withdrawn for further processing las will be described.

The predominantly aromatic lubricating oil fraction introduced into distillation zone 35 by line 33 is distilled to recover as an overhead fraction toluene concentrate which is withdrawn by line 39 and introduced back into tank 3 by way of branch line im which connects into line 35. It is understood, of course, that distillation zone 35, like distillation zone 32, is provided with all auxiliary equipment necessary for such distillation operation. 'Ihe predominantly aromatic lubricating oil components in admixture with naphthenic hydrocarbon fractions are withdrawn from zone 35 by line 4| into a stock tank i2 from whence the aromatic lubricating oil components may be withdrawn for further processing as will be described.

The predominantly saturated lubricating oil components `in tank 38 are alternately charged by line 43 containing valve 44 and pump 65 into a second adsorption zone 48 which contains a bed of activated carbon 4'! indicated generally by the shaded portion. The flow of the saturated lubricating oil components through adsorption zone 46 is alternated with now of a paraflinic hydrocarbon which is Withdrawn from tank l and introduced into zone 46 by line 49 containing pump 50 and controlled by valve 5! The substantially saturated lubricating oil components in tank 33 are charged to the zone 46 until the `capacity of the activated carbon therein for adsorbing the paraifins and the single ring naphthenes which are more strongly held on the activated carbon Y than the condensed ring naphthenes has been utilized. When the Acapacity of the activated carbon has been utilized Afor adsorbing the paranins and the single ring naphthenes, flow into adsorption zone 46 from tank 38 is interrupted by shutting down pump 45 and closing valve 44; then now from tank 48 is initiated by starting up pump 56 and opening up valve As a result the condensed naphthenes which have a very low viscosity index and are not as strongly adsorbed as the more paraflinic materials appear in the eiiluent from Zone 46 prior to the better quality lubricating oil fractions which are more paraffinic in nature. As a result of alternating the flow of the fraction from tank38 with the paraf- .nic hydrocarbons in tank 46, there are withdrawn from zone 45 by line 52 controlled by valve 53 third and fourth fractions which are in" troduced, respectively, by line 54 controlled by valve 55 into distillation zone 5G and by line 5! controlled by valve 58 into distillation zone 55. The fraction in line 54 is the third fraction which contains condensed ring lubricating oil naphthenic hydrocarbon fraction and the parafnic hydrocarbon fraction While the fraction in line 55 is 'the `fourth fraction which contains parafnic and single ring Ynaphthenic lubricating oil ,components `as Well as naphthenic ,hydrocarbon and paraiiinic hydrocarbon fractions.

It is to be understood that distillation zones 56 and 59 are similar to distillation zones 32 and 35 and are provided with all auxiliary equipment needed for all such operations.

By operating distillation zone 56 the parafnic hydrocarbon fraction being of a lower boiling point than the naphthenic boiling fraction is Withdrawn overhead from Zone 5S `by linevil and is discharged thereby back into tank 48 for reuse in the process. A fraction containing condensed ring lubricating oil components and naphthenic hydrocarbon fraction is discharged by line 6! into a distillation zone 62 where a separation ismade between the condensed ring naphthenic lubricating `oil components and the naphthenic hydrocarbon fraction, the latter being recovered by line 63 as an overhead fraction and returned by line 64 to tank `is; for reuse in Lthe process as has been described, the condensed `ring naphthenic lubricating oil components `being discharged from the system by line 65 for further use as may be desired.

The parafnic lubricating oil fraction containing the single ring naphthenic lubricating oil components in admixture with naphthenic and parainic hydrocarbon fractions is distilled in zone 59 to remove as an overhead fraction the parafnic hydrocarbon fraction by line 66 which connects into line 6l! and returns the parainic hydrocarbon fraction to tank 4B While the vparaffinic and single ring aromatic lubricating oil components are withdrawn from zone 59 by line 6l for further processing as will be described.

The predominantly aromatic hydrocarbon eluent from adsorption zone I9 which is contained in tank 4 and is an admixture of aromatic lubricating oil components and naphthenic solvent is withdrawn by line 68 containing pump 69 and valve 'l0 Vand routed into line 'H which introduces the admixture into a third adsorption zone 'l2 which is provided with a bed 13 of alumina gel indicated generally by the shaded portion. Alternately to the charge of the aromatic lubricating oil material contained in tank 42 there is charged to the adsorption zone T2 the toluene concentrate contained in tank 23 which is routed to zone 12 by line 24 which connects into line 14 controlled by valve 15 which, in turn, connects into line 1|. By alternately charging the toluene concentrate and the aromatic lubricating oil components in tank 42, it is possible to separate the aromatic lubricating oil components into a fraction containing condensed ring aromatic lubricating oil components and a fraction containing single ring lubricating oil components. The alumina gel in bed 73 will selectively adsorb the condensed ring aromatic lubricating oil components which will allow a separation. By charging alternately to the charge of the aromatic lubricating oil components the toluene concentrate, it is possible to desorb the adsorbed material from the alumina gel and to obtain fth and sixth fractions from the adsorption zone l2. Thus the effluent discharged by line i6 may be separated into a fifth fraction which is introduced by line 'l1 controlled by valve 18 into a distillation zone 19. The fifth fraction will contain the single ring aromatic lubricating oil components, toluene concentrate and naphthenic hydrocarbon solvent. A sixth fraction which contains condensed ring aromatic 'lubricating oil cornponents, toluene concentrate and la naphthenic fraction is routed by line 80 controlled by valve 8| into a distillation zone 82. Distillation zones 'I9 and 82 are like the other distillation zones in that they are provided with all auxiliary equipment necessary for such operations. In distillation zone 19 conditions are adjusted to remove the toluene concentrate as an overhead fraction by line 83 for recycling to tank 23 as will be described further. A fraction containing single ring aromatic lubricating oil components and naphthenic hydrocarbon fraction is withdrawn from distillation zone 'I9 by line 84 for further processing as will be described.

The condensed ring lubricating oil components introduced into zone 82 by line 80 is also distilled by adjustment of conditions in zone 82 to allow recovery of the toluene concentrate as an overhead fraction by line 85. As Will be noted, line 83 ties into line 85. Line 85 connects into line 4|] which, in turn, connects to line 36 allowing the return of the toluene concentrate to tank 23. The condensed ring aromatic lubricating oil components and naphthenic hydrocarbon fraction is withdrawn from zone S2 by line 86 which introduces this material into a distillation zone 8l which is like the other distillation zones and is employed to separate the naphthenic hydrocarbon fraction from the condensed ring aromatic lubricating oil components. The conditions are adjusted in zone 81 to remove the naphthenic hydrocarbon fraction by line 8S which connects into line 89 and thence with line 9U which allows the naphthenic hydrocarbon fraction to be returned by line 64 to tank i6 for reuse in the process.

The condensed ring aromatic lubricating oil components are withdrawn from the system by line 9| and thereafter used as a cracking stock or as a feed stock to a hydro-dealkylation unit.

The fractions withdrawn from Zones 59 and 19, which are the fourth and fifth fractions, by lines G1 and 84 are admixed and introduced by line 92 into still another distillation Zone 93 which is like the other distillation zones which have been described. Conditions are adjusted in zone 33 to remove as overhead fraction` the naphthenic hydrocarbon solvent by line 94 which connects into line 90 allowing the naphthenic hydrocarbon fraction to be routed by line 64 to tank I6. The iinished lubricating oil of high viscosity index is withdrawn from zone 93 by line 95. This lubricating oil consists substantially of only single ring aromatic hydrocarbons and single ring naphthenic hydrocarbons and parafnic hydrocarbons, the condensed ring naphthenic and aromatic hydrocarbons having been discarded as has been described.

A feature of the present invention is employing porous adsorbents which will separate among the v-arious types of hydrocarbons in a lubricating `oil fraction. Another feature of the invention is employing hydrocarbon fractions for use as diluents and desorbing agents which have divergent boiling points such that the viscosity of the lubricating oil fraction is reduced and such that the adsorbents are regenerated by alternately iowing the aromatic hydrocarbons fraction and the parafuic hydrocarbon fraction through the beds of porous adsorbent as has been described. By virtue of the divergent or different boiling points, it is possible to make a separation among the various hydrocarbons separated as to types as provided in our invention.

Suitable feed stocks for the practice of the present invention are, for example, lubricating oil Table Vol. Percent V' I Total Fraction 91. 4 Separate fractions:

Parafnic and naphthenic 60 124 Condensed naphthenic 10 47 Single ring aromatic 8 95 Condensed ring aromatic 22 38 to -81 It will be seen from these data that by blending together the paraiiinic and naphthenic fraction, which has a viscosity index of 124, and the single ring aromatic fraction having a viscosity index of 95, a lubricating oil of extremely high viscosity index may be obtained in good yield. By the conventional process of phenol extraction, it is not possible to raise the V. I. of such a distillate appreciably above 100, regardless of the severity of the extraction. For example, a V. I. of about will be obtained when phenol extracting such a stock to about 60% yield.

The nature and objects of the present, invention having been completely described and illustrated, what we wish toclaim as new and useful and to secure by Letters Patent is:

1. A method for producing a high viscosity index lubricating oil which comprises separating by adsorption on silica gel a lubricating oil fraction containing parafnic, single and condensed ring naphthenic and single and condensed ring aromatic components into a rst fraction containing predominantly saturated lubricating oil components and -a second fraction containing predominantly aromatic lubricating oil components, separating by adsorption on activated carbon the first fraction into a third fraction containing condensed ring naphthenic lubricating oil components and a fourth fraction containing paraiiinic and single ring naphthenic lubricating oil components, separating by adsorption on activated alumina the second fraction into a fifth fraction containing single ring aromatic lubricating oil components and a sixth fraction containing condensed ring aromatic lubricating oil components, combining said fourth and fifth fractions and recovering from said combined fourth and fifth fractions a lubricating oil of high viscosity index.

2. A method for producing a high viscosity lubricating oil which comprises alternately charging to a bed of silica gel a lubricating oil fraction containing parainic, single and condensed ring naphthenic, and single and condensed ring aromatic hydrocarbons and an aromatic hydrocarbon fraction of a boiling point lower than that of the lubricating oil fraction, alternately recovering from the bed of silica gel a rst fraction containing predominantly saturated lubricating oil components and a second fraction containing predominantly aromatic lubricating oil components, alternately charging to a bed of activated carbon the iirst fraction and a paraffinic hydrocarbon fraction of a boiling point lower than that of the aromatic hydrocarbon fraction,

alternately recovering from the bed of activated carbon a third fraction containing condensed ring naphthenic lubricating oil components and a fourth fraction containing paraffinic and single ring naphthenic lubricating oil components, alternately charging to a bed of alumina gel the second fraction and an aromatic hydrocarbon fraction having a boiling point lower than the lubricating oil fraction, alternately recovering from the bed of alumina gel a fifth fraction containing single ring aromatic lubricating oil components and a sixth fraction containing condensed ring aromatic lubricating oil components, combining said fourth and fifth fractions, and recovering from said combined fourth and fifth fractions a lubricating oil of high viscosity index.

3. A method in accordance with claim 2 in Which the aromatic hydrocarbon fractions alternately charged to the bed of silica gel and alumina gel are identical.

4. A method for producing a high viscosity lubricating oil which comprises alternately charging to a bed of silica gel a lubricating oil fraction containing parainic, single and condensed ring naphthenic, and single and condensed ring aromatic hydrocarbons in admixture with a naphthenic hydrocarbon solvent of a boiling point lower than the lubricating oil fraction and an aromatic hydrocarbon fraction of a boiling point lower than that of the lubricating oil fraction and and lower than that of the naphthenic hydrocarbon fraction, alternately recovering from the bed of silica gel a first fraction containing predominantly saturated lubricating oil components and a second fraction containing predominantly aromatic lubricating oil components, alternately charging to a bed of activated carbon the first fraction and a parainic hydrocarbon fraction of a boiling point lower than that of the aromatic hydrocarbon fraction, alternately recovering from the bed of activated carbon a third fraction containing condensed ring naphthenic lubricating oil components and a fourth fraction containing parainic and single ring naphthenic lubricating oil components, alternately charging to a bed of alumina gel the second fraction and an aromatic hydrocarbon fraction having a boiling point lower than the lubricating oil fraction, alternately recovering from the bed of alumina gel a fifth fraction containing single ring aromatic lubricating oil components and a sixth fraction containing condensed ring aromatic lubricating oil components, combining said fourth and fifth fractions and recovering from said combined fourth and fth fractions a lubricating oil of high viscosity index.

5. A method in accordance with claim 4 in which the naphthenic hydrocarbon fraction boils in the range between 100 and 360 F., the aromatic hydrocarbon fraction is a toluene concentrate boiling in the range between 90 and 320 F. and the paraiiinic hydrocarbon boils in the range between and 310 F.

ALBERT T. WATSON. SAM H. HASTINGS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,395,491 Mavity Feb. 26, 1946 2,564,717 Olsen Aug. 21, 1951 2,572,866 Jones Oct. 30, 1951 2,576,525 Lipkin Nov. 27, 1951 

2. A METHOD FOR PRODUCING A HIGH VISCOSITY LUBRICATING OIL WHICH COMPRISES ALTERNATELY CHARGING TO A BED OF SILICA GEL A LUBRICATING OIL FRACTION CONTAINING PARAFFINIC, SINGLE AND CONDENSED RING NAPHTHENIC, AND SINGLE AND CONDENSED RING AROMATIC HYDROCARBONS AND AN AROMATIC HYDROCARBON FRACTION OF A BOILING POINT LOWER THAN THAT OF THE LUBRICATING OIL FRACTION, ALTERNATELY RECOVERING FROM THE BEDOF SILICA GEL A FIRST FRACTION CONTAINING PREDOMINANTLY SATURATED LUBRICATING OIL COMPONENTS AND A SECOND FRACTION CONTAINING PREDOMINANTLY AROMATIC LUBRICATING OIL COMPONENTS, ALTERNATELY CHARGING TO A BED OF ACTIVATED CARBON THE FIRST FRACTION AND A PARAFFINIC HYDROCARBON FRACTION OF A BOILING POINT LOWER THAN THAT OF THE AROMATIC HYDROCARBON FRACTION, ALTERNATELY RECOVERING FROM THE BED OF ACTIVATED CARBON A THIRD FRACTION CONTAINING CONDENSED RING NAPHTHENIC LUBRICATING OIL COMPONENTS AND A FOURTH FRACTION CONTAINING PARAFFINIC AND SINGLE RING NAPHTHENIC LUBRICATING OIL COMPONENTS, ALTERNATELY CHARGING TO A BED OF ALUMINA GEL THE SECOND FRACTION AND AN AROMATIC HYDROCARBON FRACTION HAVING A BOILING POINT LOWER THAN THE LUBRICATING OIL FRACTION, ALTERNATELY RECOVERING FROM THE BED OF ALUMINA GEL A FIFTH FRACTION CONTAINING SINGLE RING AROMATIC LUBRICATING OIL COMPONENTS AND A SIXTH FRACTION CONTAINING CONDENSED RING AROMATIC LUBRICATING OIL COMPONENTS, COMBINING SAID FOURTH AND FIFTH FRACTIONS, AND RECOVERING FROM SAID COMBINED FOURTH AND FIFTH FRACTIONS A LUBRICATING OIL OF HIGH VISCOSITY INDEX. 